Artificial Teeth
Good matching often requires that the shade and translucency of the artificial tooth should vary from the tip of the crown to the gingival area
. There should be good attachment between the artificial teeth and the denture base. The introduction of artificial teeth into the base should not adversely affect the base material. That is, the artificial tooth and base materials should be compatible. The two materials which are commonly used for the production of artificial teeth areAcrylic resins and
Porcelain.
Acrylic resins
Acrylic resin artificial teeth are produced in reusable metal moulds using either the dough moulding technique or by injection moulding in which the acrylic powder is softened by heating and forced into the mould under pressure. The resins used are highly cross-linked in order to produce artificial teeth which are resistant to crazing. The main difference between the materials and those used for denture base construction is the incorporation of tooth-coloured pigments rather than pink ones.
Porcelain
The composition and manipulation of porcelain are dealt with in Chapter 11. Artificial porcelain teeth are produced to standard shapes and sizes by using moulds which are approximately 30% larger than required, in order to allow for shrinkage during firing. Small holes or metal pins are incorporated in the base of the porcelain teeth during their production. These are used to give mechanical attachment to the denture base.
Properties
Both acrylic and porcelain teeth can be made to give a realistic appearance. The slightly greater translucency and depth of colour achieved with porcelain possibly gives this material a slight advantage in terms of aesthetics. Both materials are produced to a variety of shapes, sizes, colours and shades which enable selection of teeth to suit most individuals. One aspect of porcelain teeth which is sometimes unpopular with patients is the clicking sound which is made when two porcelain teeth come into contact. Attachment of the teeth to the base is through a chemical union in the case of acrylic teeth and by mechanical retention for porcelain teeth. For both materials, adequate bonding is achieved only if all traces of wax from the trial denture are removed from the teeth during the boiling out stage.
Chemical bonding of the acrylic teeth depends on the softening of the resin at the base of the teeth with monomer from the dough of denture base material. Some manufacturers encourage this process by constructing the base and core of the artificial teeth from uncross-linked or only lightly cross-linked resin which is more readily softened. The outer enamel layers of the tooth are constructed from highly cross-linked resin to prevent crazing. Unfortunately it may be necessary to remove these lightly cross-linked areas when trimming denture teeth to fit into the space available within the dentures. It can then be very difficult to achieve an adequate attachment to the remaining highly cross-linked material.
The appearance of both porcelain and acrylic teeth can be customized using surface stains. Those for porcelain teeth are similar to the glaze stains used for porcelain crown and bridge materials. Their use necessitates the teeth being placed through a glazing cycle by a ceramic technician. The surface stains for acrylic are applied in the form of a surface lacquer. Both approaches can produce a dramatic increase in the realism of denture teeth. However, the effect of acrylic surface stains is rather short-lived as the lacquer is soft and hence worn away quite rapidly.
by: calsmile12 A Look At How Trips To The Dentist Are Made Easier For Patients In Morganville, Nj Cosmetic Dentistry Which Often Includes Teeth Whitening Choosing The Best Austin Dentist Orthodontist Washington DC The Truth About Teeth Whitening Dentist Directory Why Do People Grind Their Teeth How To Find The Best Philadelphia Dentist Best Teeth Whitener is the One That You Use In Your Mouth! Fort Worth Cosmetic Dentist Could You Benefit from Teeth Whitening Strips? Endodontics In Primary Teeth Cosmetic Dentist Houston -financing Cosmetic Dentistry Dentists did not Hurt David The Role Of A Cosmetic Dentist